#include <iostream>
#include <string>

std::string const name[] = {"chest", "biceps", "back"};
int count[3];
int n;

int main()
{
	std::cin >> n;
	for (int i = 0; i < n; i++) {
		int x; std::cin >> x;
		count[i % 3] += x;
	}
	int max = -1, p;
	for (int i = 0; i < 3; i++)
		if (count[i] > max) {
			max = count[i];
			p = i;
		}
	std::cout << name[p] << "\n";
}

